High-work-hardening-ratio hot rolling Q&P steel plate and preparing method thereof

Abstract

The invention relates to a high-work-hardening-ratio hot rolling Q&P steel plate and a preparing method thereof. According to the technical scheme, the high-work-hardening-ratio hot rolling Q&P steelplate comprises chemical components including, by weight percent, 0.15 to 0.20% of C, 0.60 to 1.0% of Si, 1.2 to 2.0% of Mn, 0.03 to 0.06% of Al, 0.03 to 0.06% of Nb, not larger than 0.020% of P, notlarger than 0.005% of S and the balance Fe and inevitable impurities. A casting blank is placed in a heating furnace, the charging temperature ranges from 700 DEG C to 900 DEG C, heating to 1180 DEG Cto 1230 DEG C is achieved, heat preservation is carried out for 50 to 90 min, heavy reduction is carried out in the first three passes, the reduction rate ranges from 40 to 60%, the final rolling temperature ranges from 800 DEG C to 880 DEG C, cooling to 650 DEG C to 720 DEG C is achieved, air cooling relaxation is carried out for 4 to 8 s, ferrite is precipitated, cooling to 340 DEG C to 400 DEGC is achieved, partition treatment is carried out, the partition treatment time is 10 to 60 s, water quenching to the room temperature is achieved, and the high-work-hardening-ratio hot rolling Q&P steel plate is obtained. The process is simple, the cost is low, and the made product is high in work hardening rate, good in mechanical property, high in strength and ductility product and excellent in forming performance.

Description

technical field [0001] The invention belongs to the technical field of hot-rolled Q&P steel plates. In particular, it relates to a hot-rolled Q&P steel plate with a high work hardening rate and a preparation method thereof. Background technique [0002] In recent years, with the advancement of automobile energy-saving and emission-reduction technologies, especially the development of new energy vehicles, automobile lightweight has become a development trend, and the demand for thin-gauge high-strength automobile steel is increasing. Advanced high-strength steels such as dual-phase steels (DP), transformation-induced plasticity steels (TRIP), martensitic steels (MART), twinning-induced plasticity steels (TWIP), quench-partition steels (Q&P) and hot-formed steels all have high Its weight reduction potential, high crash safety performance and high formability have won the favor of steel manufacturers and automobile users. The first-generation automotive steel has low plastici...

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Problems solved by technology

[0004] At present, high-strength Q&P steel sheets for automobiles often need to add precious metal elements such as Cr, Mo and Ni to control the transformation of supercooled austenite, which significantly increases the production cost

Moreover, the existing high-strength steel for automobiles achieves high strength while obtaining a low initial work hardening rate n value, which is not conducive to the stamping and forming of structural parts

"A quenching and annealing preparation method for ultra-high-strength thin steel plates for automobiles" (CN102943169A) patented technology, this technology reheats the obtained cold-rolled plates to the austenite zone for 20 minutes, and then cools to the two-phase zone for 1200s for a partition , and then cooled to 400°C and held for 200s for secondary distribution. Although high-strength automotive steel containing ferrite is obtained, the entire process takes a long time and is difficult to achieve large-scale production, and the strength-plastic product is not high; "a tensile strength 780MPa-grade hot-rolled dual-phase steel plate and its manufacturing method" (CN10291244A), although the process of this technology is simple, but the addition of Cr and Ti in the composition increases the production cost, and the strength-plasticity product and work-hardening rate n value are relatively high; "A preparation method of high-strength steel by hot rolling and on-line heat treatment" (CN104032109A), although the strength and plasticity obtained by this technology are relatively high, the content of C, Si and Mn is high, and the temperature needs to be raised again after hot rolling and quenching Keep warm for 10 minutes in the two-phase area, high production cost and low production efficiency

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